Magnetic recording medium

ABSTRACT

A method for magnetically recording/reproducing comprising recording an information signal by forming a pattern of a soft magnetic material in a magnetic recording medium; providing a magnetoeletric converting element in a place neighboring a face of forming the pattern of the magnetic recording medium on which the pattern is formed, applying a magnetic field to the pattern; and reproducing the information by detecting a variation of the magnetic field caused by the pattern of the soft magnetic material of the magnetic recording medium while relatively moving the magnetoelectric converting element and the magnetic recording medium.

This application is a divisional, of application Ser. No. 08/506,871,filed Jul. 25, 1995, now U.S. Pat. No. 5,703,733.

BACKGROUND OF THE INVENTION

The present invention relates to a magnetic recording/reproducing methodusing a soft magnetic material in which magnetization direction is notused as a recording means. More particularly, the present inventionrelates to a magnetic recording/reproducing method, reproducingapparatus used therefor, a magnetic recording medium and a method forproducing the same capable of recording an information signal by meansof a pattern of soft magnetic material, and capable of easily making alarge number of copies of the same information.

In the technical field of an optical disc or a magnetic recordingapparatus, as a result of highly developed information-relatedtechniques, a technique for mass recording data is increasinglyimportant. Further, tracking servo techniques for positioning arecording head are indispensable for the purpose of recording data withhigh density.

An optical disc is an example of achieving the afore-mentioned needswith low cost. In the case of producing the optical disc, a master dischaving concave parts and convex parts called a guiding groove, guidingpit or the like for necessary data or a servo is prepared by means of alaser direct drawing technique with high precision in the masteringprocess, followed by transfering the master disc to a plastic disc bymeans of injection molding, so that mass production can be achieved. Thereason why the concave parts and the convex parts are reproduced in theoptical disc with good condition, or servo operation can be performed byusing the concave parts and the convex parts with good condition ismarked change of intensity of the light beam reflected on the concaveparts and the convex parts caused by diffraction

Further, as seen in a video tape recorder, floppy disc and the like, ina magentic recording apparatus, copies of mass recorded data can bemade. However, in magnetic recording, magnetic patterns of informationshould be written one by one by using the magnetic head, said patternbeing composed of fine magnetics. Therefore, it is impossible to makesuch a large amount of copies that are performed by the optical disc.For that reason, copies in magnetic recording tend to be expensive. Inthe tracking servo of magnetic head, the pattern, which should beprecisely written by the magnetic head on the magnetic medium, isusually used. There arises such a problem that the patterns are movedfrom the predetermined position by vibration or the like when the servopatterns are written.

On the other hand, convex parts and concave parts using the magnetichead in the magnetic disc has been performed. For instance, as disclosedin "Digest of the Intermag conference, Paper #FD-10, Stockholm Sweden(April, 1993)" or "Japanese Association of Promoting Science, the 144thcommittee of magnetic recording, the document number 104 (Nov. 25,1993)", an address mark or a pit for positioning is prepared by the samemethod as the optical disc, followed by reading the convex parts andconcave parts by the magnetic head (referring to FIG. 16).

In this method, the following two means are employed for the purpose ofreading a slight change of magnetic flux caused by the magnetization ofthe convex parts and a concave parts of the magnetic head 41 such asshown in FIG. 16.

One is optimizing the shape of a slider (not shown in FIG. 16) carryingthe head portion so that spacing of about 0.1 μm even on the convexparts and the concave parts can be stably obtained.

The other is recording by using the magnetic head so that themagnetization directions of a concave part and a convex part areanti-parallel with each other as shown in FIG. 17(b). In thisspecification anti-parallel means that the magnetization directions areopposed to each other in the same plane. For example, the magnetizationdirections of the concave parts and the convex parts are made to alignin the same direction by applying an initial large magnetic field asshown in FIG. 17(a). This is followed by applying a small magnetic fieldso that only in the convex parts magnetization directions are reversedas shown in FIG. 17(b). By virtue of the magnetic head with spacingsubstantially the same as the difference between a height of the convexpart and a height of the concave part, a large magnetic field can beapplied to the convex part and small magnetic field can be applied tothe concave part. Even in the magnetic head, a large signal can beobtained by making the magenetization directions of the convex parts andthe concave parts anti-parallel to each other.

By using the above-mentioned method, there arises no such a problem thatthe patterns are moved from the predetermined position by the vibrationin case of writing a servo pattern. For that reason, the servo operationcan be performed in good condition. However, even in the method of usingthe convex parts and the concave parts, the magnetic patterns should berecorded by using a hard magnetic material in the surface, followed byapplying a magnetic field.

Further, there is disclosed the other apparatus in Japanese UnexaminedPatent Publication No. 77615/1974. As shown in FIG. 18, the apparatuscomprises a permanent magnet 43, a Hall element 44, a magnetic member 45made of a material having high permeability and a thin magnetic film 46made of a material having high permeability. Since the apparatus is usedfor reproducing of magnetic card, a large pattern of several hundredmicro meters to 1 mm is reproduced. For that reason, in the apparatusthere is provided first and second gaps in a magnetic circuit. The Hallelement is located in the first gap interposed between the permanentmagnet 43 and the magnetic member 45. Between the permanent magnet 43and the magnetic member 45, there is formed the second gap for detectingthe thin magnetic film. The magnetic circuit is formed with interposingthe gaps. When the thin magnetic film comes near the second gap betweenthe permanent magnet and the magnetic member where the card is located,a large amount of the magnetic flux flows in the Hall element. While onthe other hand, when the thin magnetic film is not located in the placenear the second gap, there is a small flow of the magnetic flux flowinginto the Hall element since a magnetic reluctance is large in themagnetic circuit. The large and small magnetic fluxes flowing into theHall element are transformed to a large and small Hall voltage as anelectric signal.

According to the conventional apparatus provided with the convex partsand the concave parts on the magnetic disc, it is required to keep themagnetic head floating with spacing of about 0.1 μm. For that reason, itis required to make the recording medium and the magnetic head close forthe purpose of avoiding an effect caused by fine particle such as dust,so that it is impossible to exchange the recording medium. Further, inorder to make the magnetization directions of the convex parts and theconvave parts anti-parallel to each other, it is required to employ themagnetic head for writing a magnetization. Therefore, there is a problemin which the many copies each having information identical with eachother will be produced with increased cost. Further, there arises theproblem that the magnetic patterns are erroneously cancelled by aneffect of the external magnetic field since the magnetic patternswritten on the magnetic medium are employed as information.

On the other hand, the conventional apparatus using a Hall elementincludes an insulating film formed on both sides of the Hall element andthe first gap with spacing of at least 100 μm to several hundred micrometers for the purpose of connecting with a lead or lead wire. For thatreason, the magnetic reluctance in the magnetic circuit becomes large.When the spacing of the second gap located in the side of the card(recording medium) is small, changing of the Hall voltage depending onthe presence of the thin magnetic film is small, and a desired SN ratiois difficult to obtain. Accordingly, the spacing of the gap on the cardside is required to range between several hundred micro meters to about1 mm, so that the information with high density cannot be reproduced.

The object of the present invention is to solve the above-mentionedproblem, and to provide a magnetically recording/reproducing method inwhich a large number of copies can be easily made in the same manner asan optical disc, and so in which information with high density can berecorded and reproduced while using magnetism.

Another object of the present invention is to provide a magneticreproducing apparatus used for the above-mentioned magneticallyrecording/reproducing method in which information with high densityrecorded in a magnetic recording medium can be surely reproduced fromthe magnetic recording medium.

Yet another object of the present invention is to provide a magneticrecording medium and method for the same in which a large amount ofcopies can be made and information can be recorded with high density.

SUMMARY OF THE INVENTION

These and other objects are realized in the present invention, which inone aspect is a magnetically recording/reproducing method including thesteps of:

recording an information signal by forming a pattern of a soft magneticmaterial in a magnetic recording medium;

providing a magnetoelectric converting element in a place neighboring aface of forming said pattern of said magnetic recording medium;

applying a magnetic field to said magnetoelectric converting element;and

reproducing said information by detecting a variation of said magneticfield caused by presence or absence of said soft magnetic material basedon said pattern of said soft magnetic material of said magneticrecording medium while relatively moving said magnetoelectric convertingelement and said magnetic recording medium.

In another aspect, magnetically recording/reproducing method includes astep where information signal is reproduced by providing a magnetic headcomprising a magnetic circuit including a magnet and magnetic gap, and amagnetoelectric converting element provided in said magnetic gap suchthat said magnetic gap of said magnetic head faces to said magneticrecording medium, and by detecting a variation of a magnetic flux insaid magnetic gap caused by that said pattern of said soft magneticmaterial approaches to said magnetic gap by said relatively moving.

Another feature of the magnetically recording/reproducing method maybethat said information signal is reproduced by applying said magneticfield in a direction vertical with respect to said magnetic recordingmedium, and detecting a variation of the direction of magnetic fieldpassing through said magnetoelectric converting element caused by thatsaid pattern of said soft magnetic material approaches to saidmagnetoelectric converting element by said relatively moving.

Recording of the information may be performed by forming a pattern of asoft magnetic material, causing a magnetoeletric converting element toapproach said magnetic recording medium, applying magnetic field, andrelatively moving said magnetic recording medium and saidmagnetoelectric converting element.

For that reason, the presence or absence of a soft magnetic materialbased on said pattern sequentially approaches to said magnetoelectricconverting element or separates from said magnetoelectric convertingelement such as an MR element film due to the relative movement. In theapplied magnetic field, when the soft magentic material is located in aplace near the magnetoelectric converting element, the magneticreluctance of said soft magenetic material is smaller than that of saidmagnetoelectric material when there is not any soft magnetic material.Therefore, the magnetic flux is easily concentrated, and the magneticfield is bent.

When the magnetic field is applied to an MR film, the magneticreluctance hardly changes even if the magnetic field is applied in adirection perpendicular to said MR film. On the other hand, there is avariation of the magnetic reluctance in the case of applying themagnetic field having a component in the direction parallel to said MRfilm.

Therefore, the variation of the magnetic field can be seen if only avoltage or an electric current between both ends of the MR film ismeasured. As a result, the information such as spacing of adjacentpatterns can be seen, and the information can be reproduced. Further,the recording of the information is formed by means of the pattern ofsoft magnetic material, so that the information cannot be influenced byexternal magnetic field, and high reliability can be achieved.

The magnetoelectric converting element may be provided in the magneticgap in the magnetic circuit such that the magnetoelectric convertingelement is arranged in a place neighboring the pattern of the softmagnetic material in the magnetic recording medium. Accordingly, themagnetic flux completely passes through the magnetoelectric convertingelement provided within the magnetic gap if the pattern of the softmagnetic material is not located in a place neighboring the magneticgap, whereas the most part of the magnetic flux passes through the softmagnetic material having a small magnetic reluctance, and the magneticflux never passes the magnetoelectric converting element if the patternof the soft magnetic material is located under the magnetic gap due tothe relatively moving. As a result, a variation of the electricresistance of the magnetoelectric converting element can be detected,and the information of the pattern of the soft magnetic material can bereproduced.

The magnetic field applied to the magnetic recording medium in thedirection perpendicular to the magnetic recording medium is bent in theside of the pattern of the soft magnetic material in such a case thatthe soft magnetic material is close to the pattern of the soft magneticmaterial. For that reason, the magnetic flux passing through themagnetoelectric converting element is directed in the directionperpendicular to the magnetic recording medium if the pattern of thesoft magnetic material is located apart from the magnetoelectricconverting element, whereas a part of the magnetic flux is bent in theside of the pattern of the soft magnetic material when the pattern ofthe soft magnetic material comes near the magnetoelectric convertingelement, so that magnetic reluctance of the magnetoelectric convertingelement is varied and the patterns of the informations of soft magneticmaterial can be reproduced.

A magnetic reproducing apparatus of the present invention comprises: atable for loading a magnetic recording medium in which informationsignals are recorded, a magnetoelectric converting element provided in aplace neighboring said magnetic recording medium loaded on said table, amagnet applying a magnetic field to at least said magnetoelectricconverting element, and a means for relatively moving said table andsaid magnetoelectric converting element.

In accordance with the magnetic reproducing apparatus of the presentinvention, the magnetoelectric converting element is provided in amanner as to be close to the magnetic recording medium, magnetic fieldcan be applied and the magnetic recording medium and the magnetoelectricconverting element can be relatively moved. Accordingly, theinformations recorded in the magnetic recording medium by the patternsof soft magnetic material can be precisely reproduced due to theabove-mentioned function.

A magnetic recording medium of the present invention comprises: asubstrate, and at least one pattern formed on the surface of thesubstrate by the soft magentic material, said pattern corresponding tothe information signal.

In accordance with the magnetic recording medium of the presentinvention, information are recorded by the patterns of the soft magneticmaterial. For that reason, the informations can be reproduced easily andsurely by the magnetoelectric converting element and applied magneticfield. Further, informations are recorded by the soft magnetic material.Therefore, there happens no erroneously delete or variation caused byexternal magnetic field, the informations can be easily copied since theinformations are not recorded by magnetization.

A method for producing a magnetic recording medium of the instantinvention comprises: providing a soft magnetic material film on asurface of a substrate, said film being any one of a soft magnetic thinfilm, fine particles or leaf, and forming a pattern of a soft magneticmaterial corresponding to an information signal by etching said softmagnetic material film.

A method for producing a magnetic recording medium of another aspect ofthe instant invention comprises: forming a plastic substrate on whichconcave and convex are formed corresponding to an information signal byinjection molding, and providing a soft magnetic material film on wholesurface of said substrate.

A method for producing a magnetic recording medium of still anotheraspect of the instant invention comprises a step of forming concave andconvex corresponding to an information signal by stamping on a surfaceof a substrate, at least said surface of said substrate being made ofsoft magnetic material.

In accordance with the method for producing the magnetic recordingmedium of the instant invention, the patterns of the soft magneticmaterial are formed, so that even a extremely fine pattern can beprecisely formed. In accordance with the method for producing themagnetic recording medium of another aspect of the instant invention,the plastic substrate on the surface of which the concave and the convexare formed is easily formed by injection moulding, the soft magneticmaterial is formed on the surface by sputtering or vacuum evaporation.For that reason, the patterns of the concave and the convex can beeasily formed. In accordance with the method for producing the magneticrecording medium of still another aspect of the instant invention, theconcave and the convex are formed by stamping, so that the concave andthe convex can be easily and precisely formed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a magneticallyrecording/reproducing method of example 1 of the present invention;

FIG. 2(a) and FIG. 2(b) are an explanatory view explaining anoperational principle of FIG. 1;

FIG. 3 is a diagram illustrating a relation between spacing S betweenmagnetoelectric converting element and magnetic recording medium andoutput of magnetoelectric converting element of example 1;

FIG. 4 is a perspective view illustrating a magneticallyrecording/reproducing method of example 2 of the present invention;

FIGS. 5(a), 5(b) and 5(c) are each explanatory views illustrating anoperational principle of FIG. 4;

FIG. 6 is a perspective view illustrating a magneticallyrecording/reproducing method of example 3 of the present invention;

FIG. 7 is a diagram illustrating an operational principle of FIG. 6;

FIG. 8 is an explanatory view illustrating a relation betweenmagnetoelectric converting element and track;

FIG. 9 is a perspective view showing one example of magnetoelectricconverting element divided into two parts;

FIG. 10 is a diagram showing a circuit for processing a tracking servosignal and a reproducing signal;

FIG. 11 is a fragmentary sectional view showing one example of magneticrecording medium;

FIG. 12 is a fragmentary sectional view showing another example ofmagnetic recording medium;

FIG. 13 is a fragmentary sectional view showing still another example ofmagnetic recording medium;

FIG. 14 is a perspective view showing another example of reproducingapparatus of the present invention;

FIG. 15 is a perspective view showing still another example ofreproducing apparatus of the present invention;

FIG. 16 is an explanatory view showing a conventional magneticallyrecording/reproducing method in which convex parts and concave parts areformed on the surface of magnetic recording medium;

FIGS. 17(a) and 17(b) are each explanatory view illustrating a methodfor writing an information according to the method of FIG. 16; and

FIG. 18 is a conventional magnetically recording/reproducing methodusing a Hall element.

DETAILED DESCRIPTION

A magnetically recording/reproducing method, magnetic reproducingapparatus, magnetic recording medium and method for producing the sameare described with reference to Figures.

The magnetically recording/reproducing method of the present inventionis characterized in that an information signal is recorded by forming apattern of soft magnetic material in a magnetic recording medium a, amagnetoelectric converting element is provided in a place neighboringthe recording medium on which the pattern is formed and a magnetic fieldis applied, and the information signal recorded in the magneticrecording medium is reproduced by detecting a variation of the magneticfield depending on presence or absence of the pattern (i.e. existing ornon-existing of the pattern) of the soft magnetic material of therecording medium while moving the magnetic recording medium relative tothe magnetoelectric converting element.

Further, magnetic reproducing apparatus of the present inventionincludes a table for loading the magnetic recording medium, amagnetoelectric converting element provided in a place neighboring themagnetic recording medium loaded on the table, a magnet applying amagnetic field to at least a part of the magnetoelectric convertingelement, and a means for moving the magnetoelectric converting elementrelative to the table for loading.

Furthermore, in accordance with the magnetic recording medium of thepresent invention, the magnetic recording medium is provided with apattern corresponding to the information signal formed by a softmagnetic material on the surface of the substrate. A signal for trackingservo can be written at the same time.

In accordance with the present invention, the magnetoelectric convertingelement is provided in a place neighboring the magnetic recordingmedium, a variation of the magnetic field passing through themagnetoelectric converting element due to the moving of the pattern ofthe soft magnetic material formed on the magnetic recording medium isdetected, so that the information recorded in the magnetic recordingmedium is read in the form of the electric signals transformed by themagnetoelectric converting element. That is, the variation of themagnetic field due to the pattern of the soft magnetic material isdirectly detected by the magnetoelectric converting element neighboringthe pattern. Accordingly, even a fine pattern can be precisely read withhigh sensitivity. In this respect, the method in accordance with thepresent invention is quite different from the conventional method inwhich the magnetic pattern located in one gap in the magnetic circuit isused as a part of the magnetic circuit, and a Hall element is providedin another gap in the magnetic circuit, thereby the variation of themagnetic flux in the magnetic circuit is read.

For that reason, in accordance with the conventional method, absence orpresence of the magnetic material should be repeated by the lengthlarger than the length of the another gap of the magnetic circuit inwhich the Hall element is provided, and the magnetic material of thepattern should be made in such a manner that a size of the magneticmaterial is more than several hundred micro meters.

Further, in accordance with the present invention, the magnetoelectricconverting element is provided in a place neighboring the magneticrecording medium. Accordingly, it is not necessary to provide themagnetoelectric converting element in a place located apart from themagnetic recording medium via the magnetic circuit, and the patterns canbe detected with high sensitivity without any influence of attenuationdue to the magnetic circuit.

Further, in accordance with the present invention, the pattern of thesoft magnetic material is not used as a part of the magnetic circuit.Accordingly, recorded information can be read out when the magneticfield is applied even if the magnetic head in which any closed magneticcircuit is formed is not used.

As the method for applying the magnetic field, one method is to providea magnetoelectric converting element in the gap formed in a part of themagnetic circuit as shown in FIG. 1, and form the magnetic flux flowingin the direction parallel to the magnetic recording medium, and detect avariation of the magnetic flux due to the pattern of the soft magneticmaterial, and the other is to apply the magnetic field in the directionperpendicular to the magnetic recording medium, and detect the variationdue to bending of the magnetic flux in the place neighboring the patternby means of the pattern of the soft magnetic material.

A permanent magnet or an electric magnet can be used as the magnet. Thepermanent magnet is superior because of an electric power not to beapplied, whereas the electric magnet is superior because of the magneticfield strength capable of adjusting. As the magnetoelectric convertingelement which converts a variation of the magnetic field into anelectric signal, magnetoresistive converting element (hereinafterreferred to as an MR element), a giant magnetoresistive convertingelement (hereinafter referred to as a GMR element), a Hall element orthe like can be employed. In view of a sensitivity of the magnetic field(a rate of change of electric resistance relative to unit of change ofmagnetic field), the MR element or the GMR element is preferablyemployed.

The means for relatively moving the magnetoelectric converting elementincludes a motor for driving a magnetic recording medium and a mechanismfor fixing a center of the medium to a driving shaft of the motor whenthe magnetic recording medium is a circular disc. Further, the meansincludes a linear motor for moving a medium or a head when the magneticrecording medium is a rectangular card.

The magnetic recording medium 1 can be formed into a pattern 3 of thesoft magnetic material partially formed with corresponding to theinformation signal on the substrate made of non magnetic material suchas plastic, aluminum, glass as shown in FIGS. 1 or 4. Further, wholesurface of the magnetic recording medium may be covered with the softmagnetic material as shown in FIGS. 11 or 13, and the surface is formedinto concave parts and convex parts. Thereby, the concave parts and theconvex parts can be used as a pattern of the soft magnetic material. Inthis case, if a vertical difference between the concave part and theconvex part is about 1 μm, the concave part is located apart from themagnetoelectric converting element, so that the concave part functionsas if there were not any soft magnetic material.

Furthermore, when the soft magnetic material is partially formed on thesubstrate as mentioned before, in FIGS. 1 or 4 the soft magneticmaterial is buried in the concave part formed on the substrate made ofnon magnetic material. However, the soft magnetic material may be formedon the surface of the substrate so as to form a convex In this case, asshown in FIG. 12, the pattern can be projected by etching to expose thenon magnetic substrate. The projected portions (i.e. the convex parts)can be flat by forming a protecting film on the surface.

The soft magnetic material for forming a pattern of the informationsignal generally means a material having a large relative permeability.The material of which relative permeability is not smaller than 50 ispreferably employed. As the soft magnetic material, Fe--Ni, Fe--Ni--Co,Ni--Co, Fe--Si--Al, Co--Fe--Si--B, Co--Zr--Nb, Fe--Ta--N, Fe--Zr--N orthe like can be employed.

In accordance with the method of claim 4, the information signals of aplurality of tracks are reproduced simultaneously by providing aplurality of magnetoelectric converting elements, thereby achieving areproducing speed of several times as fast as the reproducing speed ofthe conventional method. Continuous output can be kept by storing thereproduced informations of the following tracks in a memory or the like,then reproducing all of the preceeding informations, followed byoutputting the informations.

Tracking servo may be performed while reproducing the recordedinformations, thereby constantly modifying of the track and correctlydetecting on the track can be performed. As a result, correctinformations with small noise can be reproduced.

The information may be detected by dividing a magnetoelectric convertingelement divided into two parts. For that reason, each of said two partscan detect a half of the track.

When the magnetoelectric converting element is correctly positioned onthe track, one output from one of said two parts is identical with theother output from the other of said two parts. When the magnetoelectricconverting element is not positioned on the track, there is generated adifference between two detecting signals. Therefore, tracking servo canbe performed by correcting the track in such a manner that the onedetecting signal is equal to the other detecting signal of themagnetoelectric converting element divided into two parts. Further, therecorded information can be reproduced by using a signal of summing bothtwo detecting signals.

The magnetic head in which the magnetoelectric converting element may beprovided within the gap is provided such that the magnetic gap is closeto the magnetic recording medium. Therefore, the information of themagnetic recording medium can be precisely reproduced by theabove-mentioned effect.

The magnetic head may include a magnet and a magnetoelectric convertingelement provided in either of magnetic poles of said magnet. Therefore,variation of the magnetic field, which is caused by the patterns of thesoft magnetic material of the magnetic recording medium, can be detectedand reproduced.

The magnet can be provided in a manner as to be positioned apart fromthe magnetic head. For that reason, the magnetic head is composed ofonly a magnetoelectric converting element. However, the variation ofmagnetic field caused by the magnet positioned apart from the magnetichead can be detected, and the information of the magnetic recordingmedium can be reproduced.

A plurality of the magnetoelectric converting elements may be provided.For that reason, the informations of a plurality of the tracks can bereproduced simultaneously, or tracking servo can be performed whilereproducing said informations.

Any one of an MR element, a GMR element or a Hall element may beemployed as a magnetoelectric converting element, so that even a slightchange of the magnetic field can be surely detected.

The magnetoelectric converting element may be divided into two parts sothat recorded information of track width are divided into two parts,each of which can be detected. For that reason, tracking servo can beperformed more easily by comparing one of said two with the other.

A lead wire can be formed in a manner as to extend in the same directionas the direction of film of either the MR film or the GMR film As aresult, the magnetic head can be easily produced.

The patterns for tracking servo may be formed so that tracking servo canbe performed while reproducing of the informations.

The patterns may be formed by existing or non-existing of the softmagnetic material, so that variation of the magnetic field caused by thepatterns can be surely obtained.

The patterns may be formed by concave and convex parts of the surface ofthe soft magnetic material. The concave parts are positioned apart fromthe magentoelectric element, so that the concave parts are notinfluenced by the magnetic flux, whereas the convex parts are positionedin a place close to the magnetoelectric converting element, so that themagnetic flux passing through the magnetic converting element is bent tocause a variation. The patterns formed by the concave and the convex canbe copied by stamping or press working with large quantity, and aresuitable for mass-production.

The patterns may be formed on the surface of the substrate by providingthe soft magnetic material film For that reason, plastic or the like canbe used as a substrate because it easily forms the concave and theconvex surfaces. Further, in the case of using a bulk material of thesoft magnetic material the patterns can be formed by stamping ormoulding.

The surface may be made to be flat by forming a protecting film, so thatthere exists no such a concave and a convex. Therefore, fine particlesuch as dust can not be easily stuck on the surface.

EXAMPLE 1

In FIG. 1, numeral 1 denotes a magnetic recording medium The magneticrecording medium 1 comprises a plastic substrate 2, a pattern 3 made ofsoft magnetic material and a protecting film 4. The magnetic recordingmedium without the protecting film 4 can be employed. Numeral 5 denotesa magnetic head comprising a yoke type permanent magnet 6, an MR film 7and a lead 8 for detecting a variation of electric resistance of the MRfilm 7.

In the present embodiment, the magnetic circuit is formed in whichmagnetic gap is formed in a place for providing the MR film 7. Themagnetic field is applied in the magnetic gap in the direction parallelto the magnetic recording medium 1 and the MR film 7, and the magneticflux is applied through the MR film.

The magnetic reproducing apparatus comprises a magnetic head including ayoke type magnet and a magnetoelectric converting element, a table (notshown) for loading the magnetic recording medium which is provided insuch a manner that the magnetoelectric converting element is close tothe magnetic recording medium and a means (not shown in FIGS.) forrelatively moving the table and the magentoelectric converting element.

By virtue of forming a soft magnetic material film on both side faces ofthe magnetic head 5 to form a magnetic shield, the influence of theother pattern adjacent to the pattern can be prevented, or the influenceof an external magnetic field can be prevented, so that a resolution ofthe magnetic head can be increased, or an external noise can be reduced.

In turn, the operation will be explained. In FIG. 1, the magneticrecording medium is moved by the means for relatively moving (not shownin FIGS.) under the static magnetic head 5. Please note that the casewhere the magnetic head moves on the static magnetic recording medium 1is identical in principle. Further, both the magnetic recording medium 1and the magnetic head 5 can move. The important thing is that themagnetic head should be moved relative to the magnetic recordingmedium 1. In this case the patterns of the soft magnetic material formedon the surface of the magnetic recording medium 1 pass under themagnetic head 5 one after another.

The magnetic flux density applied to the MR film 7 from the permanentmagnet 6 is varied by the relation of the relative location of themagnetic head 5 and the pattern 3 of the soft magnetic material as shownin FIG. 2. Firstly, when there is a pattern 3 just under the magnetichead 5 as shown in FIG. 2(a), almost all of the magnetic flux from thepermanent magnet 6 flows in the pattern 3 of the soft magnetic material.It is the reason therefor that the pattern 3 of the soft magneticmaterial formed on the surface of the magnetic recording medium 1 ismade of a material through which the magnetic flux is easily passed. Onthe other hand, when the pattern of the soft magnetic material islocated in the place located apart from the magnetic head 5 as shown inFIG. 2(b), the whole part of the magnetic flux from the permanent magnet6 flows in the MR film 7. As described above, if the relative relationof location between the magnetic head 5 and the pattern 3 of the softmagnetic material varies, magnetic flux density (i.e., the magneticfield) passing through the MR film 7 is remarkably varied. The electricresistance of the MR film 7 varies depending on changing of the magneticflux density. For that reason, the changing of the electric resistancecan be detected by a variation of a voltage or an electric currentapplied to both ends of the lead 8. That is, it can be detected as anelectric signal whether there is the soft magnetic material based on thepattern 3 of the soft magnetic material formed on the surface of themagnetic recording medium 1.

In FIG. 3, there is shown the relation between a relative value of anamplitude of signal (output) obtained by the apparatus and a spacing Sfrom the magnetic head 5 to the pattern 3 of the soft magnetic material.In this case, the pattern 3 of the soft magnetic material has a completeperiodic pattern of which period is 2 μm. A relative velocity betweenthe magnetic head 5 and the magnetic recording medium 1 is 1 m/second.Further, the signal is obtained as a curve approximating to a sine waveof which frequency is 500 kHz. As seen from FIG. 3, the spacing was aslarge as about half of the period of pattern 3 of the soft magneticmaterial. The spacing was about 1 μm.

In accordance with the present example, the medium which is recordedwith high density can be reproduced with large spacing in goodcondition.

In example 1, the permanent magnet 6 was employed as a magnet. The sameproperty can be obtained by employing an electric magnet instead of thepermanent magnet 6. Further, the MR film 7 was employed as a detectorfor detecting a variation of the magnetic field (magnetic flux density).However, the variation of the magnetic field caused by the pattern 3 ofthe soft magnetic material can be detected by providing a GMR filminstead of the MR film 7 or providing a Hall element or the like.

The magnetic recording medium 1 can be copied with lower cost by using amaster disc called as a stamper. A method of producing the stamper willbe explained briefly.

A photoresist of about 500 nm is applied to a substrate having highsmoothness of surface by means of spin coat. The substrate is exposed byusing a concentrated laser beam after pre-bake. The beam can beconcentrated to have a concentration of about submicrons. Further, byvirtue of having a galvanomirror or a mechanism for transferring thesubstrate with high precision, even in extremely fine pattern exposurecan be attained. After exposure, the pattern having a desired depth canbe formed on the glass substrate by developing for a suitable time. Forexample, weak laser beam is irradiated to a portion of the developingglass disc. By virtue of advancing of the development, patterns comeout. As the patterns come out, the intensity of diffracted light becomesincreasingly high. A direction of irradiating a primary diffracted lightcan be calculated by a pitch of the pattern. Accordingly, a photo sensoris arranged to be directed in said direction. The intensity of theprimary diffracted light corresponds to the depth of the pattern withone to one. For that reason, by virtue of monitoring the intensity ofthe primary diffracted light, the development can be stopped when thearbitrary depth is obtained. In turn, an electric conductive materialsuch as Ni, Cu is vacuum-evaporated on the pattern so as to have athickness of about 10 nm Followed by plating on the conductive materialsuch as Ni, Cu using an electric field plating so as to have a thicknessof about 500 82 m. By removing the plated portion from the glasssubstrate, the stamper can be obtained in the removed plated portion. Byvirtue of carefully selecting a plating condition, the fine patternprepared on the glass substrate can be precisely transcribed on thestamper. If need be, the stamper is subjected to an outer diameterformation or an inner diameter formation.

In the case of copying the magnetic recording medium 1 using thestamper, there are some methods as follows:

The stamping is performed with high pressure directly applying to aplastic substrate on which the soft magnetic leaf or foil made of amaterial such as Fe--Ni, Fe--Ni--Co, Ni--Co is applied, or the softmagentic thin film is covered by vacuum evaporation or sputtering. A pitis made by directly stamping the soft magnetic plate without employingany plastic substrate, thereby recording medium writing informations bythe pattern of the concave part and the convex part is found to performa good characteristic.

As described hereinafter in the following example, the plastic substratein which concave parts and convex parts are formed is prepared from thestamper as well as an optical disc by means of injection moulding, andon the substrate there can be formed a soft magnetic film by coating,vacuum evaporation or sputtering to have a thickness of about 0.03 μm toabout 3.0 μm. There is also a method in which fine particles of softmagnetic material are applied.

The magnetic recording medium can be reproduced with low cost and massproduction by producing in such a method.

Further, in accordance with the other method, the leaf or foil made ofthe soft magnetic material or soft magnetic thin film provided on thesubstrate made of non magnetic material such as plastic is subjected topatterning to form a pattern of the soft magnetic material, thenmagnetic recording medium is obtained.

EXAMPLE 2

As shown in FIG. 4, the example 2 is characterized in that the magnetichead 11 having a rectangular parallelepiped shape or an ellipticcylindrical shape comprises a permanent magnet 12 magnetized in thevertical direction and an MR film 7 with interposing an insulating film13 between the permanent magnet 12 and the MR film 7 on the side of oneof the magnetic poles. The MR film 7 is formed on the surface of themagnetic head 1 of the permanent magnet 12.

In accordance with elements constituting the example 2, there is not anyclosed magnetic circuit. The magnetic field is applied from one end ofthe permanent magnet to the magnetic recording medium 1. In said one endof the permanent magnet, there is provided the MR film 7, and themagnetic flux penetrates the MR film vertically.

The magnetic reproducing apparatus of example 2 comprises a magnet, amagnetic head including a magnetoelectric converting element such as theMR film 7 formed on one end of said magnet, a table (not shown) forloading the magnetic recording medium wherein the magnetoelectricconverting element is provided in a place neighboring the magneticrecording medium, and a means (not shown) for relatively moving thetable and the magnetoelectric converting element.

The operation will be explained with reference to FIG. 5. In example 2,the magnetic flux from the permanent magnet applied to the MR film 7varies depending on the relation of the location between the magnetichead 11 and the pattern 3 of the soft magnetic material. As shown inFIG. 5(a), when the pattern 3 of the soft magnetic material ispositioned just under the MR film 7, in the MR film the magnetic fluxfrom the permanent magnet 12 has only a vertial component against aplane of the MR film 7. On the other hand, when the pattern 3 of thesoft magnetic material is positioned in a place deviated from the placejust under the MR film 7 to right or left direction as shown FIG. 5(b)or 5(c), the magnetic field having a component of the right or the leftdirection is applied to the MR film 7. In the MR film 7, there is notsubstantial variation of electric resistance to the magnetic fieldvertical to the surface of the MR film 7. However, there is a largevariation of electric resistance to even a small change of the magneticfield in the MR film 7. Also in this case, it can be verified whetherthere is a pattern 3 or not. That is, the information recorded as thepattern 3 of the soft magnetic material in the magnetic recording medium1 can be reproduced in good condition.

In accordance with the example 2, the change of the magnetic fieldapplied to the MR film can be reproduced with high sensitivity, and widespacing can be achieved.

EXAMPLE 3

As shown in FIG. 6, the magnetic head 11a of example 3 comprises an MRfilm 7 having a lead 8 and a substrate 9. A permanent magnet (or anelectric magnet) 12a is positioned just over the magnetic head 11a withbeing apart from a distance (several mili-meter to about 1 cm), orpositioned in a place with interposing a magnetic recording medium 1. Inthis case, the permanent magnet is large. The magnetic field generatedfrom the permanent magnet is uniformly applied to a broad range, forexample, a range of about 1 cm. The direction of the magnetic field issubstantially vertical to the magnetic recording medium 1.

Example 3 is different from example 2 in the point that the permanentmagnet is provided without being integrated with the magnetic head 11a.The closed magnetic circuit is not formed in example 3, and the magneticfield is applied in the direction vertical to the magnetic recordingmedium 1 like example 2.

The magnetic reproducing apparatus of example 3 comprises a magnetichead including a magnetoelectric converting element such as the MR film7, a table (not shown) for loading a magnetic recording medium, a magnetcapable of applying a magnetic field in the vertical direction, and ameans (not shown) for relatively moving like examples 1 and 2.

In turn, the operation of example 3 will be explained with reference toFIG. 7. The permanent magnet 12a is large compared with the magnetichead 11a. For that reason, as shown in FIG. 7, the homogeneous magneticfield is applied to not only the magnetic head 11a but also asurroundings thereof in the direction vertical to the magnetic recordingmedium (please note that the lines marked arrows show each magneticflux). However, in the neighbourhood of the pattern 3 of the softmagnetic material in the magnetic recording medium, the magnetic flux isconcentrated in the patterns, and the direction of the flux turns asshown by Q in FIG. 7. On the other hand, as shown by P in FIG. 7, in theplace where there is not any pattern 3 of the soft magnetic material,there is not changed a magnetic flux. Therefore, by relatively movingthe magnetic recording medium 1 to the magnetic head 11a, the patterns 3pass under the magnetic head 11a one after another. Thereby thevariation of the magnetic field can be detected As a result, theinformation represented by the patterns 3 of the soft magnetic materialformed on the magnetic recording medium 1 can be reproduced.

In accordance with example 3, uniform magnetic field is applied to themagnetic recording medium 1 provided with patterns 3 of the softmagnetic material. For that reason, there is no such a noise that isgenerated in the case of moving the state of magnetization of the softmagnetic material, so that further preferable reproducing of S/N can beachieved compared with example 2.

EXAMPLE 4

Now the case where the tracking servo is subjected will be explained Anytype of the magnetic head shown in examples 1 to 3 performs the sametracking servo property. Accordingly, the research was performed byusing the magnetic head of example 2.

In FIG. 8, there is shown a relation of the location between the pattern3 of the soft magnetic material and the magnetic head 14 in one case Awhere the magnetic head is positioned just over the track, and in theother case B where the magnetic head is partially located over the trackA width of the pattern (i.e., a width of the track) W is 10 μm, and eachof the patterns is disposed periodically of which period T is 2 μm. Asshown in FIG. 9, the magnetic head 14 comprises a permanent magnet 12,MR films 15, 16 divided evenly into two parts, and leads 17, 18, 19. Aconstant electric current I_(o) is applied to the leads 17 and 19. Eachof the leads 17, 18, 19 are connected to output terminal 21 and 22 viaamplifiers 25a to 25e as shown in FIG. 10. If each value of electricresistance of the MR films 15 and 16 is Ra and Rb, respectively,(Ra+Rb)I_(o) is obtained as a summed output in the terminal 21, and(Ra-Rb)I_(o) is obtained as a subtracted output in the terminal 22. Thesummed output in the terminal 21 is connected to an amplifier 23 fordata, and the subtracted output in the terminal 22 is connected to anamplifier 24 for servo. The amplifier 23 for data has a band width of ahigh frequency zone not smaller than 1 MHz, said band width beingcapable of sufficiently detecting a variation of the magnetic flux(i.e., the information of data pit) obtained from the period (2 μm) ofthe patterns of the soft magnetic material. On the other hand, theamplifier 24 for servo has a band no more than about 1 kHz. A variationof the magnetic flux obtained from the period (2 μm) of the patterns 3of the soft magnetic material is high frequency compared with said band,so that a mean value thereof is obtained. The frequency which can bedetected by the amplifier 24 for servo is a difference from ROM pit rowof the patterns of the soft magnetic material. The difference is rangedbetween several tens hertzes and several hundreds hertzes which can bedetected by the amplifier 24 for servo.

In turn, the operation will be explained. When the magnetic head 14 islocated just over the rows of the patterns 3 of the soft magneticmaterial (see A in FIG. 8), the magnetic flux density flowing in the twoMR films 15 is identical with that in the MR film 16. For that reason,the subtracted output is 0. The more the magnetic head 14 moves from thelocation just over the rows of the patterns 3 of the soft magneticmaterial (see B in FIG. 8), the more the subtracted output deviates from0. For example, when the magnetic head 14 moves to the left, thesubtracted output becomes positive, and when the right, the subtractedoutput becomes negative. The subtracted output is observed by theamplifier 24 for servo which can make the magnetic head 14 position justover the rows of the patterns 3 of the soft magnetic material so thatthe subtracted output is 0.

EXAMPLE 5

FIG. 11 is a sectional view for illustrating an example of the patternsof the soft magnetic material provided on the surface of the magneticrecording medium In FIG. 11, numeral 26 denotes a substrate made ofplastic, glass, or the like in which the patterns are formed byphotocurable resin, numeral 27 denotes a soft magnetic material, numeral28 denotes a protecting film made of SiO₂, SiN or the like. In thiscase, the soft magnetic material 27 continuously formed on the surfaceof the recording medium 1. However, there are different distances fromthe magnetic head to the surface of the pattern depending on the concavepart and the convex part of the substrate, said magnet being provided ina place neighboring the surface of the protecting film 28, and not shownin FIG. 11, thereby effectively performing the same function as thepatterns of the soft magnetic material.

The protecting film 28 is formed by coating material having highfluidity (i.e., low viscosity) such as boro-silicated glass, photoresistor the like. Thereby flat surface of the magnetic recording medium 1without among concave part and convex part is obtained, and a breakageor deterioration caused by contacting the magnetic head with themagnetic recording medium can be surely prevented. For that reason, anapparatus having high reliability is obtained. As mentioned above, theprotecting film plays the part to improve the reliability. In view ofthe reproducing property, the effect of the invention is maintainedwithout the protecting film 28.

The patterns of example 5 can be easily obtained by forming a softmagnetic material film made of Fe--Ni, Co--Ni or the like on the wholesurface of the substrate 26, in which the concave parts and the convexparts corresponding to the information signals is formed by injectionmoulding, by means of sputtering, vacuum evaporation or the like.Further, the medium can be produced with low cost by only forming amagnetic film on the substrates which are mass-reproduced with low cost.By virtue of making the surface flat by the protecting film 28, theimprovement of reliability and further stable spacing between head andmedium can be achieved.

EXAMPLE 6

FIG. 12 is a sectional view illustrating another example of the patternsof the soft magnetic material formed on the surface of the magneticrecording medium 1. In FIG. 12, numeral 30 denotes a substrate made ofplastic, glass or the like, numeral 31 denotes a soft magnetic materialfilm. A protecting film is not shown. However, there is no differencebetween the pattern having a protecting film and the pattern withoutprotecting film The magnetic recording medium of example 6 is obtainedby forming a soft magnetic material film 31 on the substrate 30 byvacuum-evaporating or sputtering a material such as Fe--Ni, Fe--Ni--Co,or applying a thin soft magnetic material plate to the surface of thesubstrate 30, followed by removing the soft magnetic material film 31 inthe place where the concave parts are formed by patterning and etching.In accordance with example 6, etching is performed to the substrate 30for the purpose of surely removing the soft magnetic material film 31.However, etching is not necessarily performed to the substrate 30.

In accordance with example 6, there is not any soft magnetic material inthe concave parts. For that reason, the flux is turned to the convexparts strongly so that the signals become large.

EXAMPLE 7

FIG. 13 is a sectional view illustrating still another example of themagnetic recording medium 1. In FIG. 13 the magnetic recording medium 1is made of the soft magnetic material. By virtue of convex parts 32formed on the surface, the patterns of the soft magnetic material areobtained. The concave part and the convex part of the surface are formedby means of press or etching. In FIG. 13 there is not shown a protectingfilm There is no difference between the magnetic recording medium havinga protecting film and the magnetic recording medium without a protectingfilm.

In accordance with example 7, the magnetic recording medium 1 can beproduced by only stamping with low cost.

The magnetic recording medium 1 of the present invention as mentionedabove can be employed in a disc, a card, a tape or the like. On thesurface of the magnetic recording medium, servo signals as well as thesignals representing information can be written.

EXAMPLE 8

FIG. 14 is an example of the magnetic reproducing apparatus of thepresent invention in which the construction of the magnetic head ischanged. In example 8 multiple type magnetic head 33 including aplurality of magnetoelectric converting elements as shown in FIG. 14which can perform highly advanced function is employed. In FIG. 14,numeral 34 denotes a permanent magnet, numerals 35a, 35b, 35c denoteeach magnetoelectric converting element which is made of, for example,an MR film, numerals 36a, 36b, 36c denote each lead of themagnetoelectric converting elements 35a, 35b, 35c, respectively. Inaccordance with example 8, the multiple type magnetic head comprises asingle permanent magnet 34, a plurality of magnetoelectric convertingelements 35a, 35b, 35c and a plurality of leads 36a, 36b, 36c. By virtueof thus elements constituting the magnetic head of example 8,information of a plurality of tracks can be reproduced.

As a result, the amount of information which can be reproduced in unittime is increased. For that reason, time for reproducing can bedecreased. Further, the magnetoelectric converting element 35a can beemployed only for tracking servo, and the other magnetoelectricconverting elements 35b, 35c can be employed only for reproducing theinformation, so that still more stable reproducing operation can beachieved.

EXAMPLE 9

FIG. 15 is another example of magnetic reproducing apparatus of thepresent invention, in which the MR film employed in example 1 isarranged vertical to the magnetic recording medium 1. The other elementsand operation are the same as example 1.

In accordance with the elements of example 9, the MR film 7 and theleads 8 can be formed on an identical surface, so that the reproducingapparatus can be, easily produced and assembled with low cost.

According to the magnetic recording/reproducing method of the presentinvention, information can be recorded by the patterns of the softmagnetic material. For that reason, copying of the magnetic recordingmedium can be mechanically mass-produced with low cost. Further, inaccordance with the present invention, recording can be performed by thesoft magnetic material, so that influence of erroneously cancelling dueto external magnetic field can be avoided, and high reliability of themagnetic recording medium can be achieved.

Further, by virtue of the magnetoelectric converting element arranged ina place neighboring the magnetic recording medium, the patterns of thesoft magnetic material are detected, so that fine patterns on the orderof submicrons can be read by low magnetic field. For that reason, highdensity of information and precisely reproducing with small noise can beachieved.

As a result, ROM in which high density information is recorded can becommercially recorded/reproduced by magnetic device without anycomplicated apparatus such as an optical disc, a semiconductor memory.

According to the magnetic reproducing apparatus of the presentinvention, only the variation of the signal on both ends of themagnetoelectric converting element may be detected. Therefore, theapplied voltage (or electric current) may be constant. For that reason,fine patterns can be precisely detected with the simple construction.

Further, according to the magnetic recording medium and producing methodtherefor of the present invention, recording of information can beperformed by patterning of the soft magnetic material. For that reason,the pattern can be easily formed by forming a concave part and a convexpart by means of stamping or press working, providing a soft magneticmaterial film on the substrate after forming the concave part and theconvex part by injection moulding, or etching. The patterns can bemass-produced with low cost. Further, information of high density can berecorded, and cancelling of recorded information by the externalmagnetic field can be avoided.

Though several embodiments of the present invention are described above,it is to be understood that the present invention is not limited only tothe above-mentioned, various changes and modifications may be made inthe invention without departing from the spirit and scope thereof.

What is claimed is:
 1. A magnetic recording medium wherein a pattern ofsoft magnetic material corresponding to an information signal is formedon a substrate and beneath and proximate to a flat exterior surface ofsaid magnetic recording medium, wherein the presence or absence of saidpattern relative to a direction normal to said surface and along adirection of recording defines said information signal, wherein saidsubstrate is made of non-magnetic material.
 2. The magnetic recordingmedium of claim 1, wherein said soft magnetic material positioned on asubstrate is any one of a thin film provided on a surface of saidsubstrate, fine particles stuck on said surface, a leaf of material anda bulk material.
 3. The magnetic recording medium of claim 1, whereinsaid exterior surface of said substrate is formed of a protecting filmmade of a nonmagnetic material, with the exterior surface of saidprotecting film being made flat.
 4. The magnetic recording medium ofclaim 1, wherein portions of said soft magnetic material are separatedby portions of said non-magnetic material having no soft magneticmaterial formed thereon.
 5. The magnetic recording medium of claim 4,wherein said portions of said soft-magnetic material lie on portions ofsaid non-magnetic material which are closer to said surface relative tosaid portions of said non-magnetic material having no soft magneticmaterial formed thereon.
 6. A magnetic recording medium wherein apattern of soft magnetic material corresponding to an information signalis formed on a substrate and beneath and proximate to a flat exteriorsurface of said magnetic recording medium wherein a tracking servopattern of a soft magnetic material corresponding to tracking servosignal other than said information signal is further formed.
 7. Amagnetic recording medium wherein a pattern of soft magnetic materialcorresponding to an information signal is formed on a substrate andbeneath and proximate to a flat exterior surface of said magneticrecording medium, wherein the presence or absence of said patternrelative to a direction normal to said surface and along a direction ofrecording defines said information signal wherein said pattern is formedby concave and convex portions, said convex parts being located closerto said surface than said concave portions.
 8. The magnetic recordingmedium of claim 7, wherein a distance of about 1 μm separates saidconcave portions from said convex portions in a direction normal to saidsurface.